1. Field of the Invention
The present invention relates to a technique for reproducing the color of a subject with high accuracy, and in particular relates to a technique for reproducing the color of the subject under various light sources.
2. Description of the Related Art
There has recently been an increased demand for faithfully expressing the color of the subject when outputting an image. For this reason, a technique for reproducing the color of the subject under a specific light source designated as the observation environment (colorimetric color reproduction) has been developed. However, recently, a technique for reproducing the color of the subject under arbitrary environmental conditions, for example, an arbitrary light source, (spectral color reproduction) has been drawing more attention. In spectral color reproduction, an image is output such that the spectral reflectance of the subject in the output image is close to the actual spectral reflectance of the subject.
However, the types of color components that an image output apparatus such as a printing apparatus can use are limited. Therefore, it is difficult to precisely reproduce the spectral reflectance of the subject in the entire visible wavelength range. For this reason, a method for reproducing color such that the colorimetric value of the subject in the output image is close to the actual colorimetric value of the subject under a number of predetermined light sources has been proposed.
For example, in the techniques disclosed in Japanese Patent Laid-Open Nos. 2009-171556 and 2009-147632, a color difference ΔE between a target color observed under a certain light source and the color reproduced under the light source that is estimated based on the amount of color material used by the printing apparatus is calculated for a number of predetermined light sources. Then, the amount of color material is determined such that the value obtained by performing weighted addition on the color differences ΔE for each of the light sources is reduced.
The gamut that the image output apparatus is capable of outputting differs depending on the light source used in observation. However, in the techniques disclosed in Japanese Patent Laid-Open Nos. 2009-171556 and 2009-147632, no consideration is given to the gamut that the image output apparatus is capable of outputting. Accordingly, in the case where the color of the subject is out of the gamut that the image output apparatus is capable of outputting, the tones of the color of the subject may not be maintained.